Load responsive switch

ABSTRACT

A load responsive switch that is responsive, for example, to the weight of an operator or passenger on the seat of an automobile. The switch is actuated by the deflection of a composite beam comprising upper and lower metal strips which are separated by a plastic spacer. At one end of the beam, the ends of the upper and lower strips are connected to each other. At the other end of the beam, the lower strip is fixed to a housing for the switch, and the corresponding end of the upper strip is free. In this manner, when the beam is flexed in response, for example, to the weight of a driver or passenger on the seat of the automobile, the end of the upper strip moves into the switch housing to change the state of the switch. The housing is provided with a slide member movable longitudinally therein, and a cover for closing the upper portion thereof. Two terminals are contained in the housing and the switch is closed when the contact arms of a bus bar mounted in a slot in the slide member engage the terminals. The plastic slide has a central rib frictionally received between fingers on the end of the upper strip. Overtravel of the upper strip is accommodated by movement of the free end thereof relative to the sides of the central rib of the slide member.

United States Patent [191 Loose et a1.

[ Sept. 25, 1973 LOAD RESPONSIVE SWITCH [75] Inventors: Winfield Warren Loose,

Linglestown; Frederick Jean Maltais, Camp Hill, both of Pa.

[73] Assignee: AMP Incorporated, Harrisburg, Pa. [22] Filed: Sept. 17, 1971 [21] Appl. No.: 181,499

Primary ExaminerDavid Smith, Jr. Att0rneyWilliam J. Keating et a1.

[5 7 ABSTRACT A load responsive switch that is responsive, for example, to the weight of an operator or passenger on the seat of an automobile. The switch is actuated by the deflection of a composite beam comprising upper and lower metal strips which are separated by a plastic spacer. At one end of the beam, the ends of the upper and lower strips are connected to each other. At the other end of the beam, the lower strip is fixed to a housing for the switch, and the corresponding end of the upper strip is free. In this manner, when the beam is flexed in response, for example, to the weight of a driver or passenger on the seat of the automobile, the end of the upper strip moves into the switch housing to change the state of the switch. The housing is provided with a slide member movable longitudinally therein, and a cover for closing the upper portion thereof. Two terminals are contained in the housing and the switch is closed when the contact arms of a bus bar mounted in a slot in the slide member engage the terminals. The plastic slide has a central rib frictionally received between fingers on the end of the upper strip. Overtravel of the upper strip is accommodated by movement of the free end thereof relative to the sides of the central rib of the slide member.

21 Claims, 13 Drawing Figures PATENTEDSEPZSISYS SHEET 1 [IF 6 PATENTEI] SEPZS I975 SHEET 3 [IF 6 PATENTED SEPZSIQB sum u UF 6 I LOAD RESPONSIVE SWITCH BACKGROUND OF THE INVENTION ger on the seat of an automobile or the like.

Future safety requirements for automobiles will probably require a seatbelt alarm system to insure that the operator has fastened his seatbelt before operating the automobile. As presently proposed, such 'alarm systems will comprise a retracting reel for each seatbelt having a switch which will be opened or closed when the seatbelt has been pulled from the reel and attached to the other part of the belt. The system will also include a seat sensor switch supported on one or more springs of the seat which will be opened or closed when the driver or a passenger sits on the seat. In this manner, the seatbelt switch and the seat sensor switch can serve to control a seatbelt warning light and/or alarm, and possibly the ignition.

While many'different types of presently known load responsive switches could be utilized as the seat sensor switch in a seatbelt alarm or warning system, many of these switches are not completely satisfactory for such a system because of complicated construction, high cost of manufacture or unreliable operation over extended periods of time. Accordingly, a need has arisen fora simple and inexpensive load responsive or seat sensor switch which can be easily installed or mounted within an automobile seat and is reliable in operation during extended periods of time, such as the normal life of an automobile.

SUMMARY OF THE INVENTION The load responsive switch of the present invention is well suited for use as a seat sensor switch owing to its relatively simple construction, low cost of manufacture and reliability in operation. The switch generally comprises a composite beam which is supported on a spring or springs of the automobile seat. The state of the switch is changed when the driver or a passenger'sits on the seat and, in conjunction with a seatbelt switch, the seat switch can be used to control a seatbelt warning light and/or alarm, and possibly the ignition.

The composite beam comprises upper and lower metal strips which are separated by a spacer formed of plastic or another suitable material. The strips are connected to each other at one end thereof. The other end of the lower strip is fixed to a switch housing, and the corresponding end of the upper strip is free, so that when the beam is flexed in response to the weight of a driver or passenger on the seat, the end of the upper strip moves into the switch housing to open or close the switch, depending on the intended mode of operation. The housing generally comprises a cover and a slide member longitudinally movable therein. Two terminals arecontained in the housing, and the switch is closed when the contacts of a bus bar mounted in a slot in the slide member engage the edges of these terminals. The slide has a central rib that is frictionally received'between fingers on the end of the upper strip.

In one mode of operation, when the driver or passenger is not sitting on the seat and the composite beam is not flexed, the upper strip holds the slide member in its retracted position in the switch housing so that the contacts of the bus bar are out of engagement with the terminals in the switch housing. When the driver or pas senger sits on the seat and the composite beam is flexed, the upper strip moves into the housing and pushes the slide so that the contacts of the bus bar engage the terminals to close the switch. Overtravel of the upper strip is accommodated by movement of the end of the upper strip relative to the sides of the central rib of the slide, such overtravel being necessary because of the varying weights of drivers and passengers and also owing to the initial impact when a driver or passenger bounces into the seat. When the driver or passenger leaves the car, 'the slide member is immediately retracted and subsequently the end of the upper strip moves along the central rib of the slide in a direction outwardly of the housing.

In an alternate embodiment, the composite beam comprises a corrugated actuating strip disposed between upper and lower strips. All three strips are fixed at one end, such that the corrugated strip will flatten when a driver or passenger sits on the seat and'will be movable into the switch housing to actuate the switch in a manner similar to that described above.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevational view, partly in section, of the composite beam portion of a switch constructed in accordance with the principles of the present invention, showing the beam in a non-actuated condition;

FIG. 2 is a view similar to FIG. 1, showing the beam in an actuated condition; I

FIG. 3 is an exploded view in perspective, showing the components of the composite beam of the switch of the present invention;

FIG. 4 is an enlarged exploded side elevational view in section of the end portion of the upper metal strip and the housing slide member of the switch of the present invention;

FIG. 5 is a perspective view of a load responsive switch constructed in accordance with the principles of the present invention;

FIG. 6 is an enlarged exploded view in perspective of some of the components of the switch shown in FIG. 5;

FIGS. 7-10 are plan views in section of the housing of the switch of the present invention, showing various stages of operation of the switch;

FIG. 11 is a schematic view in perspective of a seatbelt warning system utilizing the switch of the present invention; and

FIGS. 12 and 13 are side elevational views of an alternate embodiment of the composite beam of the switch of the present invention, showing the beam in unflexed and flexed conditions, respectively.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 138 Referring briefly to FIG. 11 of the drawings, the load responsive switch 10 of the present invention may be utilized as a seat sensor switch in a seatbelt warning or alarm system. In such a system, the switch 10 is supported or mounted on one or more seat springs 12, 60 and is electrically connected to switches 14 that are actuated by the withdrawal of the seatbelts from the reels 16. The load responsive switch 10 and the seatbelt switches 14 may be connected to an audible alarm 18, a warning light or indicator 20 and/or the ignition 22. In this manner, the state of the seatbelt switches 14 and that of the load responsive or seat sensor switch can be used to control the audible alarm 18, the warning light 2.0 or the ignition 22, thereby insuring that the operator has fastened his seatbelt prior to operating the automobile.

As shown in FIGS. 1-3, the load responsive switch 10 of the present invention comprises a composite actuating beam 30 having an upper metal strip 32, a lower metal strip 34 and an intermediate spacer member 36 formed of any suitable material such as plastic. The upper and lower strips 32 and 34 are joined to each other at one end in any suitable manner, such as by one or more rivets 38. A plurality of clip members 40 surround the lower strip 34, the sides of the plastic spacer 36 and a portion of the upper strip 32. Each of the clips 40 is provided with an upstanding tab member 42 which extends upwardly through an opening 44 in lower strip 34 and into an oversized opening 46 in spacer 36. In this manner, the clips 40 are fixed to the lower strip 34 and the upper strip is slidable relative to the clips 40. The spacer 36 maintains the spacing between strips 32, 34 when the composite beam is flexed but, by virtue of the fact that the openings 46 in the spacer are oversized relative to the tabs 42, the spacer is flexed and stressed independent of the strips 32, 34.

The other end of the lower strip 34 is fixed in any suitable manner, such as by one or more rivets'48, to the housing 50 for the switch 10. As shown in FIG. 1, when the composite beam 30 of the switch 10 is not subjected to a downward load, the free end of the upper strip 32 is substantially in alignment with the fixed end of the lower strip 34. When the beam 30 is subjected to a downward load L, as shown in FIG. 2, which serves to deform or bend-the upper and lower strips 32 and 34, the free end of the upper strip 32 is moved inwardly into the switch housing 50 to change the state of the switch in response to the load L. The load L could be the weight of an operator or passenger sitting on the seat of an automobile or the like, in the case where the switch- 10 serves as a seat sensor switch and is mounted or supported on the seat springs 12, as shown in FIG. 11.

As shown in FIGS. 5-7, the switch housing 50 comprises a body portion 52 and a cover 54 that is adapted to fit over the top of the body portion in any suitable manner. The body portion 52 is provided with a depending wall 56 and depending tabs 58 spaced from the wall 56 for the purpose of defining a recess adapted to receive a supporting member which may be a seat spring 60 or the like. It should be noted that the housing is thus pivotally mounted on the spring wire 60, i.e., it can pivot upwardly and downwardly as viewed in FIG. 5. This feature is important to the operation of the switch by the actuator beam 30 as will be explained below.

The body portion 52 of the switch housing 50 is provided with a central recess 62 in which a slide member 64 is slidably mounted. Both the body portion 52 and the slide member 64 may be formed of any suitable material such as plastic. The body portion 52 also is provided with a second enlarged recess 66 adjacent the inner end of the recess 62 in which'an enlarged inner head portion 68 of the slide mem ber 64 is slidably re ceived. The slide member 64 is provided with a transverse slot 70 in which a bus bar 72 is mounted. The bus bar 72 comprises a pair of curved spring arms 74 which extend into transverse recesses 76in the body portion 52 of the switch housing 50. The bus bar 72 is also provided with a pair of laterally extending contact arms 78 which preferably are formed integrally with the spring arms 74 from any suitable flexible and resilient metal. Both the spring arms 74 and the contact arms 78 of the bus bar 72 extend through openings 80 in longitudinally extending walls 82 of the housing body portion 52. The walls 82 serve to define the central recess 62 in the body portion 52 in which the slide member 64 is slidably mounted.

Outside of the walls 80, the body portion 52 of the switch housing 50 is provided with a pair of longitudinally extending parallel slots 84 in which electrical terminals 86 are mounted. The electrical terminals 86 may be of any suitable construction and are connected in any suitable manner, such as by tabs 88, to the exposed ends 90 of insulated conducting wires 92. Each of the electrical terminals 86 terminates at its inner end in a generally U-shaped contact portion 94 that is positioned to be engaged by the contact arms 78 of the bus bar 72 in a manner to be more fully described hereinafter.

The slide member 64 comprises an elongated central rib 96 at its outer end which has a pair of laterally extending tabs 98 that extend parallel to and are spaced from the bottom wall 100 of the slide member. The free end of the upper strip 32 of the composite beam 30 is provided with a central slot 102 which is defined at its outer end by a pair of inwardly extending tabs 104. As shown in FIGS. 6l0, the central rib 96 of the slide member 64 is received within the slot 102 in the free end of the upper strip 32, and the tabs 104 are in frictional engagement with the sides of the slide member rib 96. The side portions of the upper strip 32 defining the slot 102 are slidably received between the laterally extending tabs 98 and the bottom wall 100 of the slide member 64. The side portions of the upper strip 32 are provided with laterally outwardly extending stop members 106 which are received within recessed portions 108 in the walls 82 of the body portion 52 of the switch housing 50. In this manner, the stop members 106 serve to limit the inward and outward movement of the upper strip 32 relative to the switch housing 50, by engagement of the stop members 106 with the portions of the walls 82 defining the recess 108.

The frictional engagement between the tabs 104 of the upper strip 32 and the sides of the slide member rib 96 causes the slide member 64 to be moved inwardly and outwardly of the switch housing 50 in conjunction with the movement of the free end of the upper strip 32, and also allows the upper strip 32 to move inwardly relative to the central rib of the slide member after it has engaged the end of the body portion 52 to thereby accommodate overtravel of the upper strip 32 without damaging the slide member 64 or the bus bar 72. The inward and outward movement of the upper strip 32 is limited by the engagement of the stop members 106 with the portions of the walls 82 defining the recesses 108 in which the stop members are disposed.

The general operation of the load responsive switch 10 of the present invention will now be described. When the composite beam 30 is not subjected to a load and thus is not flexed, the upper strip 32 will be in the position shown in FIGS. 1 and 7, wherein the upper strip 32 holds the slide member 64 in its outer position within the body portion 52 of the switch housing 50, through the frictional engagement of the tabs 104 of the upper strip with the sides of the central rib 96 of the slide member. In this position, the wall 110 of the slide member defining the inner side of the transverse slot 70 engages the bus bar 72 and holds the contact arms 78 thereof out of engagement with the terminals 94 against the force of the spring arms 74 which normally serve to urge the contact arms 78 into engagement with the terminals 94. When the composite beam 30 of the switch is not flexed, therefore, the bus bar- 72 is out of engagement with the terminals 94 and the switch 10 is in an open condition.

, When the composite beam 30 is deformed in response to a load L, as shown in FIG. 2, the free end of the upper strip 32 is moved inwardly into the switch housing 50. Owing to the frictional engagement of the tabs 104 on the upper strip 32 with the sides of the central rib 96 of the slide member 64, the slide member is moved inwardly within the body portion 52 of the housing 50 to thereby allow the spring arms 74 of the bus bar 72 to move the contact arms 78 into engagement with the terminals 94 to effect a closed condition of the switch 10, as seen in FIG. 8. As previously mentioned, the housing 50 is pivotally mounted on the spring wire 60. By virtue of this pivotal mounting of the housing and by virtue of the fact that the left hand end of the beam 30 is restrained against vertical movement in the switch housing, the housing 50 will pivot in a clockwise direction about the spring wire 60 when the beam is flexed and follow the left hand end of the beam, com pare FIGS. 1 and 2. This pivotoling movement of the housing 50 has the effect of preventing the entire beam 30 from moving out of the housing when it is flexed. The upper strip 32 of the beam will, as noted above, move relatively into the housing to change the state of the switch as noted above.

As shown in FIG. 9, when the slide member 64 engages the inner end of the slot 66 in the body portion 52 of the housing 50, the free end of the upper strip 32 can continue to move inwardly within the housing 50, since the tabs 104 of the upper strip will slide along the sides of the central rib 96 of the slide member 64. In this manner, overtravel of the upper strip 32 can be accomodated without damaging the slide member 64 or the bus bar 72. Such overtravel is necessary to compensate for the varying loads that may be applied to the composite beam 30 and the initial impact of certain loads which may be greater than the sustained load thereafter onthe composite beam. When the load L is no longer applied to the composite beam 30, the upper strip 32, owing to its resiliency, will be moved outwardly within the switch housing 50, and the slide member 64 will also be moved outwardly owing to the frictional engagement of the tabs 104 on the upper strip with the sides of the central rib 96 of the slide member. This outward movement of the upper strip 32 and the slide member 64 causes the wall 110 of the slide member to engage the bus bar 72 and to move the contact arms 78 out of engagement with the terminals 94 against the force of the spring arms 74, as shown in FIG. 10. Rightward movement of the slide member 64 beyond the position of FIG. 10 is prevented when the outer ends 69 of the head portion 68 of slide member 64 moves against the left hand ends of the contact portion 94 of the terminals 86 as shown in FIG. 10. Thereafter, the upper strip 32 continues to move outwardly relative to the slide member 64 until it returns to the position shown in FIGS. 1 and 7.

From the foregoing description, it will be readily seen that the switch 10 of the present invention is normally open, and will be closed in response to the application of a load L, such as the weight of the driver or passenget on the seat of an automobile. Within the scope of the present invention, the switch 10 could function in the reverse manner, that is, it could be normally closed when not subjected to load, and then opened in response to the application of a load L.

An alternate embodiment of the composite beam for the switch 10 is shown in FIGS. 12 and 113. In this alter- I nate embodiment, the composite beam 30 comprises a corrugated metal actuating strip 33' which is positioned between an upper strip 32' and a lower strip 34'. Both the upper strip 32' and the corrugated strip 33' are fixed to the lower strip 34' at one end thereof. The other ends of the upper strip 32' and the corrugated strip 33' are free and extend into the housing 50 which is substantially the same as the housing 50 shown in FIGS. 5 and 7-10. The other end of the lower strip 34' is fixed to the housing 50' in any suitable manner. In operation, when the composite beam 30 is flexed in response to a load L, as shown in FIG. 13, the upper strip 32' is moved downwardly to flatten the corrugated strip 33' so that its free end moves inwardly within the housing 50 to change the state of the switch in response to the load L. What is claimed is: l. A load responsive switch, comprising: a housing having circuit opening and closing means, a composite beam, said composite beam comprising first and. second, normally unflexed, flexible and resilient strips, said first and second strips being secured together at one end, said first strip being free at the other end thereof and extending into said housing for actuation of said circuit opening and closing means, said second strip being secured at the other end thereof to said housing, said first strip being an elongated corrugated strip, said second strip being an elongated substantially flat strip, and a third elongated substantially flat strip extending over said first strip on the side thereof opposite to that adjacent said second strip, said third strip being secured at one end to said one end of said second strip, whereby when said first and second strips are flexed in response to the application of a load on said composite beam, the free end of said first strip is moved inwardly within said housing to actuate said circuit opening and closing means, and when said load is removed from said composite beam, said first and second strips return to their unflexed positions. 2. A load responsive switch, comprising: a housing having circuit opening and closing means, a composite beam, said composite beam comprising first and second, normally unflexed, flexible and resilient strips and an elongated spacer disposed therebetween, said first and second strips being secured together at one end, said first strip being free at thc'other end thereof and extending into said housing for actuation of said circuit opening and closing means, said second strip being secured at the other end thereof to said housing,

said circuit opening and closing means including a slide member slidably mounted within said housing, said free end of said first strip being in slidable frictional engagement with said slide member such that said slide member is movable with the free end of said first strip when it is flexed, and the free end of said first strip is movable relative to said slide member when the movement of said slide member in said housing is stopped, a pair of terminals mounted within said housing, said slide member having a transverse slot, and

a bus bar mounted within said transverse slot and having a pair of contact arms adapted to engage said terminals when said slide member is in a first position in said housing,

whereby when said first and second strips are flexed in response to the application of a load on said composite beam, the free end of said first strip is moved inwardly within said housing to actuate said circuit opening and closing means, and when said load is removed from said composite beam, said first and second strips return to their unflexed positions.

3. The switch'of claim 2 wherein said housing comprises a pair of transverse recesses, and said bus bar comprises a pair of spring arms mounted within said transverse recesses, said spring arms urging said contact arms in a direction for engagement with said terminals 4. The switch of claim 3 wherein, when said first strip is unflexed, said slide member is in a second position within said housing wherein it is in engagement with said bus bar to prevent said contact arms from engaging said terminals, and when said first strip is flexed in response to the application of a load on said composite beam, said slide member is moved to said first position in said housing wherein the contact arms of said bus bar are urged into engagement with said terminals by said spring arms.

5. A load responsive switch, comprising: a housing having circuit opening and closing means, a composite beam, said composite beam comprising first and second, normally unflexed, flexible and resilient strips and an elongated spacer disposed v therebetween, said first and second strips being secured together at one end, said first strip being free at the other end thereof and extending into said housing for actuation of said circuit opening and closing means, said second strip being secured at the other end thereof to said housing,

said circuit opening and closing means including a slide member slidably mounted within said housing, said free end of said first strip being in slidable frictional engagement with said slide member such that said slide member is movable with the free end of said first strip when it is flexed, and the free end of said first strip is movable relative to said slide member when the movement of said slide member in said housing is stopped, said slide member having a central rib, and

the free end of said first strip having a longitudinal slot therein that is defined at its outer end by a pair of inwardly extending tabs, said tabs being in frictional sliding engagement with said rib of said slide member,

whereby when said first and second stripsare flexed in response to the application of a load on said composite beam, the free end of said first strip is moved inwardly within said housing to actuate said circuit opening and closing means, and when said load is removed from said composite beam, said first and second strips return to their unflexed positions.

6. The switch of claim 5 wherein the free end of said first strip is provided with stop means engageable with said housing to limit the inward and outward movement of said free end within said housing.

7. The switch of claim 6 wherein said stop means comprise a pair of tabs extending laterally outwardly from the free end of said first strip, and said housing comprises longitudinally extending recesses in which said stop tabs are movable.

8. A load responsive switch, comprising:

a housing,

a slide member longitudinally slidable in said housing, said slide member having a central rib and a transverse slot,

a pair of terminals mounted in said housing,

a bus bar mounted in said transverse slot of said slide member and having a pair of contact arms positioned for engagement with said terminals, and

a composite beam, said composite beam comprising first and second, normally unflexed, flexible and resilient strips and an elongated spacer disposed therebetween, said first and second strips being secured together at one end thereof, said first strip being free at the other end thereof and extending into said housing in slidable frictional engagement with said central rib of said slide member, and said second strip being secured at the other end thereof to said housing,

said slide member being movable within said housing between a first position wherein said contact arms of said bus bar are in engagement with said terminals and a second position wherein said contact arms are out of engagement with said terminals,

whereby when said first and second strips are flexed in response to the application of a load on said composite beam, the free end of said first strip is moved inwardly within said housing to move said slide member to said first position, and when said load is removed from said composite beam, said first strip is moved outwardly within said housing to move said slide member to said second position.

9. The switch of claim 8 wherein the free end of said first strip has a longitudinally extending slot that is defined at its outer end by a pair of laterally inwardly extending tabs, said tabs being in frictional slidable engagement with the opposite sides of said central rib of said slide member.

10. The switch of claim 9 wherein the free end of said first strip is provided with laterally outwardly extending stop tabs that are engageable with said housing for limiting the inward and outward movement of said first strip within said housing.

11. The switch of claim 8 wherein said housing comprises a pair of transverse recesses, and said bus bar comprises a pairof spring arms mounted within said recesses, said spring arms serving to urge said contact arms into engagement with said terminals.

12. The switch of claim 8 wherein said first and second strips are substantially flat elongated metal strips.

13. The switch of claim 8 wherein said first strip is an elongated corrugated strip, said second strip is an elongated substantially flat strip, and a third elongated substantially flat strip extends over said first strip on the side thereof opposite to that adjacent said second strip,

said third strip being secured at one end thereof to said one end of said second strip.

14. A load responsive switch, comprising:

a housing having circuit opening and closing mens,

and a composite beam, said composite beam comprising first and second, normally unflexed, flexible and resilient strips, said first and second strips being secured together at one end, said first strip being free at the other end thereof and extending into said housing for actuation of said circuit opening and closing means, said second strip being secured at the other end thereof to said housing, said first strip being an elongated corrugated strip, said second strip being an elongated substantially flat strip,

whereby when said first and second strips are flexed in response to the application of a load on said composite beam, the free end of said first strip is moved inwardly within said housing to actuate said circuit opening and closing means, and when said load is removed from said composite beam, said first and second strips return to their unflexed positions.

15. The switch of claim 14 wherein said circuit opening and closing means comprises a slide member slidably mounted within said housing, said free end of said first strip being in slidable frictional engagement with said slide member such that said slide member is movable with the free end of said first strip when it is flexed, and the free end of said first strip is movable relative to said slide member when the movement of said slide member in said housing is stopped.

16. The switch of claim 15 wherein a pair of terminals are mounted within said housing, said slide member has a transverse slot, and a bus bar is mounted within said transverse slot and has a pair of contact arms adapted to engage said terminals when said slide member is in a first position in said housing.

17. The switch of claim 16 wherein said housing comprises a pair of transverse recesses, and said bus bar comprises a pair of spring arms mounted within said transverse recesses, said spring arms urging said contact arms in a direction for engagement with said terminals.

18. The switch of claim 17 wherein, when said first strip is unflexed, said slide member is in a second position within said housing wherein it is in engagement with said bus bar to prevent said contact arms from engaging said terminals, and when said first strip is flexed in response to the application of a load on said composite beam, said slide member is moved to said first position in said housing wherein the contact arms of said bus bar are urged into engagement with said terminals by said spring arms.

19. The switch of claim 15 wherein said slide member has a central rib, and the free end of said first strip has a longitudinal slot therein that is defined at its outer end by a pair ofinwardly extending tabs, said tabs being in frictional sliding engagement with said rib of said slide member.

20. The switch of claim 19 wherein the free end of said first strip is provided with stop means engageable with said housing to limit the inward and outward movement of said free end within said housing.

21. The switch of claim 20 wherein said stop means comprise a pair of tabs extending laterally outwardly from the free end of said first strip, and said housing comprises longitudinally extending recesses in which said stop tabs are movable. 

1. A load responsive switch, comprising: a housing having circuit opening and closing means, a composite beam, said composite beam comprising first and second, normally unflexed, flexible and resilient strips, said first and second strips being secured together at one end, said first strip being free at the other end thereof and extending into said housing for actuation of said circuit opening and closing means, said second strip being secured at the other end thereof to said housing, said first strip being an elongated corrugated strip, said second strip being an elongated substantially flat strip, and a third elongated substantially flat strip extending over said first strip on the side thereof opposite to that adjacent said second strip, said third strip being secured at one end to said one end of said second strip, whereby when said first and second strips are flexed in response to the application of a load on said composite beam, the free end of said first strip is moved inwardly within said housing to actuate said circuit opening and closing means, and when said load is removed from said composite beam, said first and second strips return to their unflexed positions.
 2. A load responsive switch, comprising: a housing having circuit opening and closing means, a composite beam, said composite beam comprising first and second, normally unflexed, flexible and resilient strips and an elongated spacer disposed therebetween, said first and second strips being secured together at one end, said first strip being free at the other end thereof and extending into said housing for actuation of said circuit opening and closing means, said second strip being secured at the other end thereof to said housing, said circuit opening and closing means including a slide member slidably mounted within said housing, said free end of said first strip being in slidable frictional engagement with said slide member such that said slide member is movable with the free end of said first strip when it is flexed, and the free end of said first strip is movable relative to said slide member when the movement of said slide member in said housing is stopped, a pair of terminals mounted within said housing, said slide member having a transverse slot, and a bus bar mounted within said transverse slot and having a pair of contact arms adapted to engage said terminals when said slide member is in a first position in said housing, whereby when said first and second strips are flexed in response to the application of a load on said composite beam, the free end of said first strip is moved inwardly within said housing to actuate said circuit opening and closing means, and when said load is removed from said composite beam, said first and second strips return to their unflexed positions.
 3. The switch of claim 2 wherein said housing comprises a pair of transverse recesses, and said bus bar comprises a pair of spring arms mounted within said transverse recesses, said spring arms urging said contact arms in a direction for engagement with said terminals.
 4. The switch of claim 3 wherein, when said first strip is unflexed, said slide member is in a second position within said housing wherein it is in engagement with said bus bar to prevent said contact arms from engaging said terminals, and when said first strip is flexed in rEsponse to the application of a load on said composite beam, said slide member is moved to said first position in said housing wherein the contact arms of said bus bar are urged into engagement with said terminals by said spring arms.
 5. A load responsive switch, comprising: a housing having circuit opening and closing means, a composite beam, said composite beam comprising first and second, normally unflexed, flexible and resilient strips and an elongated spacer disposed therebetween, said first and second strips being secured together at one end, said first strip being free at the other end thereof and extending into said housing for actuation of said circuit opening and closing means, said second strip being secured at the other end thereof to said housing, said circuit opening and closing means including a slide member slidably mounted within said housing, said free end of said first strip being in slidable frictional engagement with said slide member such that said slide member is movable with the free end of said first strip when it is flexed, and the free end of said first strip is movable relative to said slide member when the movement of said slide member in said housing is stopped, said slide member having a central rib, and the free end of said first strip having a longitudinal slot therein that is defined at its outer end by a pair of inwardly extending tabs, said tabs being in frictional sliding engagement with said rib of said slide member, whereby when said first and second strips are flexed in response to the application of a load on said composite beam, the free end of said first strip is moved inwardly within said housing to actuate said circuit opening and closing means, and when said load is removed from said composite beam, said first and second strips return to their unflexed positions.
 6. The switch of claim 5 wherein the free end of said first strip is provided with stop means engageable with said housing to limit the inward and outward movement of said free end within said housing.
 7. The switch of claim 6 wherein said stop means comprise a pair of tabs extending laterally outwardly from the free end of said first strip, and said housing comprises longitudinally extending recesses in which said stop tabs are movable.
 8. A load responsive switch, comprising: a housing, a slide member longitudinally slidable in said housing, said slide member having a central rib and a transverse slot, a pair of terminals mounted in said housing, a bus bar mounted in said transverse slot of said slide member and having a pair of contact arms positioned for engagement with said terminals, and a composite beam, said composite beam comprising first and second, normally unflexed, flexible and resilient strips and an elongated spacer disposed therebetween, said first and second strips being secured together at one end thereof, said first strip being free at the other end thereof and extending into said housing in slidable frictional engagement with said central rib of said slide member, and said second strip being secured at the other end thereof to said housing, said slide member being movable within said housing between a first position wherein said contact arms of said bus bar are in engagement with said terminals and a second position wherein said contact arms are out of engagement with said terminals, whereby when said first and second strips are flexed in response to the application of a load on said composite beam, the free end of said first strip is moved inwardly within said housing to move said slide member to said first position, and when said load is removed from said composite beam, said first strip is moved outwardly within said housing to move said slide member to said second position.
 9. The switch of claim 8 wherein the free end of said first strip has a longitudinally extending slot that is defined at its outer end by a pair of laterally inwardly extending tabs, said tabs being in frictional slidAble engagement with the opposite sides of said central rib of said slide member.
 10. The switch of claim 9 wherein the free end of said first strip is provided with laterally outwardly extending stop tabs that are engageable with said housing for limiting the inward and outward movement of said first strip within said housing.
 11. The switch of claim 8 wherein said housing comprises a pair of transverse recesses, and said bus bar comprises a pair of spring arms mounted within said recesses, said spring arms serving to urge said contact arms into engagement with said terminals.
 12. The switch of claim 8 wherein said first and second strips are substantially flat elongated metal strips.
 13. The switch of claim 8 wherein said first strip is an elongated corrugated strip, said second strip is an elongated substantially flat strip, and a third elongated substantially flat strip extends over said first strip on the side thereof opposite to that adjacent said second strip, said third strip being secured at one end thereof to said one end of said second strip.
 14. A load responsive switch, comprising: a housing having circuit opening and closing mens, and a composite beam, said composite beam comprising first and second, normally unflexed, flexible and resilient strips, said first and second strips being secured together at one end, said first strip being free at the other end thereof and extending into said housing for actuation of said circuit opening and closing means, said second strip being secured at the other end thereof to said housing, said first strip being an elongated corrugated strip, said second strip being an elongated substantially flat strip, whereby when said first and second strips are flexed in response to the application of a load on said composite beam, the free end of said first strip is moved inwardly within said housing to actuate said circuit opening and closing means, and when said load is removed from said composite beam, said first and second strips return to their unflexed positions.
 15. The switch of claim 14 wherein said circuit opening and closing means comprises a slide member slidably mounted within said housing, said free end of said first strip being in slidable frictional engagement with said slide member such that said slide member is movable with the free end of said first strip when it is flexed, and the free end of said first strip is movable relative to said slide member when the movement of said slide member in said housing is stopped.
 16. The switch of claim 15 wherein a pair of terminals are mounted within said housing, said slide member has a transverse slot, and a bus bar is mounted within said transverse slot and has a pair of contact arms adapted to engage said terminals when said slide member is in a first position in said housing.
 17. The switch of claim 16 wherein said housing comprises a pair of transverse recesses, and said bus bar comprises a pair of spring arms mounted within said transverse recesses, said spring arms urging said contact arms in a direction for engagement with said terminals.
 18. The switch of claim 17 wherein, when said first strip is unflexed, said slide member is in a second position within said housing wherein it is in engagement with said bus bar to prevent said contact arms from engaging said terminals, and when said first strip is flexed in response to the application of a load on said composite beam, said slide member is moved to said first position in said housing wherein the contact arms of said bus bar are urged into engagement with said terminals by said spring arms.
 19. The switch of claim 15 wherein said slide member has a central rib, and the free end of said first strip has a longitudinal slot therein that is defined at its outer end by a pair of inwardly extending tabs, said tabs being in frictional sliding engagement with said rib of said slide member.
 20. The switch of claim 19 wherein the free end of said first strip is provided with stop meaNs engageable with said housing to limit the inward and outward movement of said free end within said housing.
 21. The switch of claim 20 wherein said stop means comprise a pair of tabs extending laterally outwardly from the free end of said first strip, and said housing comprises longitudinally extending recesses in which said stop tabs are movable. 